Methods and devices for transcarotid access

ABSTRACT

Disclosed is an arterial access sheath for introducing an interventional device into an artery. The arterial access sheath includes an elongated body sized and shaped to be transcervically introduced into a common carotid artery at an access location in the neck and an internal lumen in the elongated body having a proximal opening in a proximal region of the elongated body and a distal opening in a distal region of the elongated body. The internal lumen provides a passageway for introducing an interventional device into the common carotid artery when the elongated body is positioned in the common carotid artery. The elongated body has a proximal section and a distalmost section that is more flexible than the proximal section. A ratio of an entire length of the distalmost section to an overall length of the sheath body is one tenth to one half the overall length of the sheath body.

REFERENCE TO PRIORITY DOCUMENT

This application is continuation of U.S. patent application Ser. No.15/210,770 entitled “METHODS AND DEVICES FOR TRANSCAROTID ACCESS” filedJul. 14, 2016, issuing on May 30, 2017 as U.S. Pat. No. 9,662,480, whichis a continuation of U.S. patent application Ser. No. 15/005,770entitled “METHODS AND DEVICES FOR TRANSCAROTID ACCESS” filed Jan. 25,2016, now U.S. Pat. No. 9,399,118, which is a continuation of U.S.patent application Ser. No. 14/575,199 entitled “METHODS AND DEVICES FORTRANSCAROTID ACCESS” filed Dec. 18, 2014, now U.S. Pat. No. 9,126,018,which is a continuation of U.S. patent application Ser. No. 14/537,316entitled “METHODS AND DEVICES FOR TRANSCAROTID ACCESS” filed Nov. 10,2014, now U.S. Pat. No. 9,241,699, which claims the benefit of priorityto U.S. Provisional Application Ser. No. 62/046,112, entitled “METHODSAND DEVICES FOR TRANSCAROTID ACCESS” filed on Sep. 4, 2014, and U.S.Provisional Application Ser. No. 62/075,169, entitled “METHODS ANDDEVICES FOR TRANSCAROTID ACCESS” filed on Nov. 4, 2014. Priority of theaforementioned filing dates is claimed and the patent applications areincorporated herein by reference in their entirety.

BACKGROUND

The present disclosure relates generally to medical methods, systems,and devices for performing endovascular interventions. Moreparticularly, the present disclosure relates to methods and systems foraccess directly into the carotid artery to perform interventionalprocedures in the treatment of vascular disease and other diseasesassociated with the vasculature.

Interventional procedures are performed to treat vascular disease, forexample stenosis, occlusions, aneurysms, or fistulae. Interventionalprocedures are also used to perform procedures on organs or tissuetargets that are accessible via blood vessels, for example denervationor ablation of tissue to intervene in nerve conduction, embolization ofvessels to restrict blood flow to tumors or other tissue, and deliveryof drugs, contrast, or other agents to intra or extravascular targetsfor therapeutic or diagnostic purposes. Interventional procedures aretypically divided into coronary, neurovascular, and peripheral vascularcategories. Most procedures are performed in the arterial system via anarterial access site.

Methods for gaining arterial access to perform these procedures arewell-established, and fall into two broad categories: percutaneousaccess and surgical cut-down. The majority of interventional proceduresutilize a percutaneous access. For this access method, a needle punctureis made from the skin, through the subcutaneous tissue and muscle layersto the vessel wall, and into the vessel itself. Vascular ultrasound isoften used to image the vessel and surrounding structures, andfacilitate accurate insertion of the needle into the vessel. Dependingon the size of the artery and of the access device, the method willvary, for example a Seldinger technique or modified Seldinger techniqueconsists of placing a sheath guide wire through the needle into thevessel. Typically the sheath guide wire is 0.035″ or 0.038″. In someinstances, a micro-puncture or micro access technique is used wherebythe vessel is initially accessed by a small gauge needle, andsuccessively dilated up by a 4 F micropuncture cannula through which thesheath guidewire is placed. Once the guidewire is placed, an accesssheath and sheath dilator are inserted over the guide wire into theartery. In other instances, for example if a radial artery is being usedas an access site, a smaller sheath guidewire is used through theinitial needle puncture, for example an 0.018″ guidewire. The dilator ofa radial access sheath is designed to accommodate this smaller sizeguidewire, so that the access sheath and dilator can be inserted overthe 0.018″ wire into the artery.

In a surgical cut-down, a skin incision is made and tissue is dissectedaway to the level of the target artery. This method is often used if theprocedure requires a large access device, if there is risk to the vesselwith a percutaneous access, and/or if there is possibility of unreliableclosure at the access site at the conclusion of the procedure. Dependingon the size of the artery and of the access device, an incision is madeinto the wall of the vessel with a blade, or the vessel wall ispunctured directly by an access needle, through which a sheath guidewire is placed. The micropuncture technique may also be used to place asheath guide wire. As above, the access sheath and sheath dilator areinserted into the artery over the sheath guide wire. Once the accesssheath is placed, the dilator and sheath guide wire are removed. Devicescan now be introduced via the access sheath into the artery and advancedusing standard interventional techniques and fluoroscopy to the targetsite to perform the procedure.

Access to the target site is accomplished from an arterial access sitethat is easily entered from the skin. Usually this is the femoral arterywhich is both relatively large and relatively superficial, and easy toclose on completion of the procedure using either direct compression orone of a variety of vessel closure devices. For this reason,endovascular devices are specifically designed for this femoral accesssite. However, the femoral artery and its vicinity are sometimesdiseased, making it difficult or impossible to safely access orintroduce a device into the vasculature from this site. In addition, thetreatment target site may be quite some distance from the femoral accesspoint requiring devices to be quite lengthy and cumbersome. Further,reaching the target site form the femoral access point may involvetraversing tortuous and/or diseased arteries, which adds time and riskto the procedure. For these reasons, alternate access sites aresometimes employed. These include the radial, brachial and axillaryarteries. However, these access sites are not always ideal, as theyinvolve smaller arteries and may also include tortuous segments and somedistance between the access and target sites.

Some Exemplary Issues with Current Technology

In some instances, a desired access site is the carotid artery. Forexample, procedures to treat disease at the carotid artery bifurcationand internal carotid artery are quite close to this access site.Procedures in the intracranial and cerebral arteries are likewise muchclosure to this access site than the femoral artery. This artery is alsolarger than some of the alternate access arteries noted above. (Thecommon carotid artery is typically 6 to 10 mm in diameter, the radialartery is 2 to 3 mm in diameter.)

Because most access devices used in interventional procedure aredesigned for the femoral access, these devices are not ideal for thealternate carotid access sites, both in length and mechanicalproperties. This makes the procedure more cumbersome and in some casesmore risky if using devices designed for femoral access in a carotidaccess procedure. For example, in some procedures it is desirable tokeep the distal tip of the access sheath below or away from the carotidbifurcation, for example in procedures involving placing a stent at thecarotid bifurcation. For patients with a low bifurcation, a short neck,or a very deep carotid artery, the angle of entry of the sheath into theartery (relative to the longitudinal axis of the artery) is very acutewith respect to the longitudinal axis of the artery, i.e. moreperpendicular than parallel relative to the longitudinal axis of theartery. This acute angle increases the difficulty and risk in sheathinsertion and in insertion of devices through the sheath. In theseprocedures, there is also risk of the sheath dislodgement as only aminimal length of sheath can be inserted. In femoral or radial accesscases, the sheaths are typically inserted into the artery all the way tothe hub of the sheath, making sheath position very secure and parallelto the artery, so that the issues with steep insertion angle and sheathdislodgement do not occur in femoral access sites.

In other procedures, it is desirable to position the sheath tip up toand possibly including the petrous portion of the internal carotidartery, for example in procedures requiring access to cerebral vessels.Conventional interventional sheaths and sheath dilators are not flexibleenough to be safely positioned at this site.

In addition, radiation exposure may be a problem for the hands of theoperators for procedures utilizing a transcarotid access site, if theworking areas are close to the access site.

SUMMARY

What is needed is a system of devices that optimize ease and safety ofarterial access directly into the common carotid artery. What is alsoneeded is a system of devices which minimize radiation exposure to theoperator. What are also needed are methods for safe and easy access intothe carotid artery to perform peripheral and neurovascularinterventional procedures.

Disclosed are methods and devices that enable safe, rapid and relativelyshort and straight transcarotid access to the arterial vasculature totreat coronary, peripheral and neurovascular disease states. The devicesand associated methods include transcarotid access devices, guidecatheters, catheters, and guide wires specifically to reach a targetanatomy via a transcarotid access site. Included in this disclosure arekits of various combinations of these devices to facilitate multipletypes of transcarotid interventional procedures.

In one aspect, there is disclosed a system of devices for accessing acarotid artery via a direct puncture of the carotid arterial wall,comprising a sheath guide wire, an arterial access sheath and a sheathdilator, wherein the arterial access sheath and sheath dilator are sizedand configured to be inserted in combination over the sheath guide wiredirectly into the common carotid artery, and wherein the sheath has aninternal lumen and a proximal port such that the lumen provides apassageway for an interventional device to be inserted via the proximalport into the carotid artery.

In another aspect, the system for accessing a carotid artery alsoincludes: an access needle, an access guide wire, and an access cannula,all sized and configured to insert a sheath guide wire into the wall ofthe carotid artery so that the arterial access sheath and dilator may beplaced either percutaneously or via a surgical cut down.

In another aspect, there is disclosed a method for treatment ofcoronary, peripheral or neurovascular disease, comprising: forming apenetration in a wall of a carotid artery; positioning an arterialaccess sheath through the penetration into the artery; and treating atarget site using a treatment device.

In another aspect, there is disclosed an arterial access sheath forintroducing an interventional device into an artery. The arterial accesssheath includes an elongated body sized and shaped to be transcervicallyintroduced into a common carotid artery at an access location in theneck and an internal lumen in the elongated body having a proximalopening in a proximal region of the elongated body and a distal openingin a distal region of the elongated body. The internal lumen provides apassageway for introducing an interventional device into the commoncarotid artery when the elongated body is positioned in the commoncarotid artery. The elongated body has a proximal section and adistalmost section that is more flexible than the proximal section. Aratio of an entire length of the distalmost section to an overall lengthof the sheath body is one tenth to one half the overall length of thesheath body.

Other features and advantages should be apparent from the followingdescription of various embodiments, which illustrate, by way of example,the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a transcarotid initial access system.

FIG. 2 shows a transcarotid access sheath system.

FIG. 3 shows a component of the transcarotid access system being used toaccess a carotid artery for a carotid artery procedure.

FIG. 4 shows an access sheath of the transcarotid access system beingused to access an internal carotid artery for an intracranial orneurovascular procedure.

FIG. 5 shows an embodiment of an arterial access sheath.

FIGS. 6 and 7 show distal regions of an arterial access sheath.

FIGS. 8-11 b show embodiments of an arterial access sheath.

FIG. 12 shows an embodiment of a dilator.

FIGS. 13 and 14 show enlarged views of the proximal region of thedilator.

FIGS. 15 and 16 show embodiments of a two part dilator.

FIG. 17 shows a distal region of a dilator having two guidewire lumens.

FIG. 18 shows a cross-sectional view of the distal region of FIG. 17.

DETAILED DESCRIPTION

Disclosed are methods, systems, and devices for accessing and treatingthe vasculature via a transcarotid access point in the region of thecarotid artery.

FIG. 1 shows a first embodiment of a transcarotid initial access system100 of devices for establishing initial access to a carotid artery forthe purpose of enabling introduction of a guide wire into the carotidartery. The access to the carotid artery occurs at an access sitelocated in the neck of a patient such as in the region of the patient'scarotid artery. The devices of the transcarotid initial access system100 are particularly suited for directly accessing the carotid arterythrough the wall of the common carotid artery.

As shown in FIG. 1, the transcarotid initial access system 100 includesan access needle 120, access guidewire 140, and micropuncture cannula160. The access needle 120, access guidewire 140, and micropuncturecannula 160 are all adapted to be introduced via a carotid puncture intothe carotid artery as further described below. The carotid puncture maybe accomplished, for example, percutaneously or via a surgical cut down.Embodiments of the initial access system 100 may be adapted towards oneor the other method of puncture, as further described below.

Upon establishment of access to the carotid artery using the initialaccess system 100, an access sheath may be inserted into the carotidartery at the access site wherein the access sheath may be part of atranscarotid access sheath system. FIG. 2 shows a first embodiment of atranscarotid access sheath system 200 of devices for inserting an accesssheath into the carotid artery over a sheath guidewire. When insertedinto the carotid artery, the access sheath enables or allowsintroduction of at least one interventional device into the carotidartery via a lumen of the access sheath for the purpose of performing aninterventional procedure on a region of the vasculature. Thetranscarotid access sheath system 200 includes an access sheath 220, asheath dilator 260, and a sheath guidewire 300. The access sheath 220,sheath dilator 260 and sheath guidewire 300 are all adapted to beintroduced via a carotid puncture into the carotid artery as furtherdescribed below. The carotid puncture may be accomplished percutaneouslyor via a surgical cut down. Embodiments of the system 200 may be adaptedtowards one or the other method of puncture, as further described below.

In an embodiment, some or all of the components of transcarotid initialaccess system 100 and the transcarotid access sheath system 200 may becombined into one transcarotid access system kit such as by combiningthe components into a single, package, container or a collection ofcontainers that are bundled together.

FIG. 3 shows the access sheath 220 being used to access a common carotidartery 310 for a carotid stenting procedure. The access sheath 220 isinserted into the common carotid artery 310 via a surgical cut down 315.As described further below, the access sheath 220 has an internal lumenwith openings at proximal and distal tips or regions of the accesssheath 220. With a distal portion of the access sheath 220 in thecarotid artery and a proximal portion external to the patient, theinternal lumen provides a passageway to insert an interventional deviceinto the artery.

FIG. 4 shows an access sheath 200 of the transcarotid access systembeing used to access an internal carotid artery 405 for an intracranialor neurovascular procedure. The arterial access sheath 200 accesses thecommon carotid artery 310 via insertion through a transcervicalpuncture. Once inserted into the common carotid artery 310, the distaltip of the access sheath 220 is advanced into the internal carotidartery ICA 320 and upward (relative to the puncture in FIG. 4) towarddistal cervical or petrous ICA 405 or beyond.

FIGS. 3 and 4 both show the arterial access sheath 220 being advancedupward through the patient's neck toward the patient's brain. In anotherembodiment, the arterial access sheath 220 may be advanced downward(relative to access locations in FIGS. 3-4) toward the patient's heartsuch as toward the aorta for example. U.S. Pat. No. 8,545,552 entitled“Systems and Methods for Transcatheter Aortic Valve Treatment” (which isincorporated herein by reference) describes exemplary methods ofdirectly inserting an access sheath into the carotid artery andadvancing an interventional device toward the aorta and ultimatelytowards the aortic valve.

Arterial Access Sheath

With reference again to FIG. 2, an embodiment of a transcarotid arterialaccess sheath 220 includes an elongated sheath body 222 and a proximaladaptor 224 at a proximal end of the elongated sheath body 222 of theaccess sheath 220. The elongated sheath body 222 is the portion of thearterial access sheath 220 that is sized and shaped to be inserted intothe artery and wherein at least a portion of the elongated sheath bodyis actually inserted into the artery during a procedure. The proximaladaptor 224 includes a hemostasis valve 226 and an elongated flush line228 having an internal lumen that communicates with an internal lumen ofthe sheath body 222. The proximal adaptor 224 may have a larger diameteror cross-sectional dimension than the sheath body 222. The hemostasisvalve 226 communicates with the internal lumen of the sheath body 222 toallow introduction of devices therein while preventing or minimizingblood loss via the internal lumen during the procedure. In anembodiment, the hemostasis valve 226 is a static seal-type passivevalve. In an alternate embodiment of the arterial access sheath 220(shown in FIG. 5) the hemostasis valve 226 is an adjustable-openingvalve such as a Tuohy-Borst valve 227 or rotating hemostasis valve(RHV). Alternately, the access sheath 220 may terminate on the proximalend in a female Luer adaptor to which a separate hemostasis valvecomponent may be attached, either a passive seal valve, a Tuohy-Borstvalve or rotating hemostasis valve (RHV).

The elongated sheath body 222 of the arterial access sheath 220 has adiameter that is suitable or particularly optimized to provide arterialaccess to the carotid artery. In an embodiment, the elongated sheathbody 222 is in a size range from 5 to 9 French, or alternately in aninner diameter range from 0.072 inches to 0.126 inches. In anembodiment, the elongated sheath body 222 is a 6 or 7 French sheath. Inan embodiment where the sheath is also used for aspiration or reverseflow, or to introduce larger devices, the sheath is an 8 French sheath.

The elongated sheath body 222 of the arterial access sheath 220 has alength from the proximal adapter 224 to a distal tip of the elongatedsheath body 222 that is suitable for reaching treatment sites located inor toward the brain relative to an arterial access site in the commoncarotid artery CCA. For example, to access a carotid artery bifurcationor proximal internal carotid artery ICA from a CCA access site, theelongated sheath body 222 (i.e., the portion that can be inserted intothe artery) of the access sheath 220 may have a length in a range from 7to 15 cm. In an embodiment, the elongated sheath body 222 has a lengthin the range of 10-12 cm. For access to a same target site from afemoral access site, typical access sheaths must be between 80 and 110cm, or a guide catheter must be inserted through an arterial accesssheath and advanced to the target site. A guide catheter through anaccess sheath takes up luminal area and thus restricts the size ofdevices that may be introduced to the target site. Thus an access sheaththat allows interventional devices to reach a target site without aguide catheter has advantages over an access sheath that requires use ofa guide catheter to allow interventional devices to the target site.

Alternately, to position the distal tip of the elongated sheath body 222more distally relative to the access site, for example to perform anintracranial or neurovascular procedure from a CCA access site, theelongated sheath body 222 of the access sheath 220 may have a length inthe range from 10 cm to 30 cm, depending on the desired target positionof the sheath distal tip. For example, if the target position is thedistal CCA or proximal ICA, the elongated sheath body 222 may be in therange from 10 cm to 15 cm. If the desired target position is the mid todistal cervical, petrous, or cavernous segments of the ICA, theelongated sheath body 222 may be in the range from 15 to 30 cm.

Alternately, the arterial access sheath 220 is configured or adapted fortreatment sites or target locations located proximal to the arterialaccess site (i.e. towards the aorta) when the access site is in thecommon carotid artery. For example the treatment site may be theproximal region of the CCA, CCA ostium, ascending or descending aorta oraortic arch, aortic valve, coronary arteries, or other peripheralarteries. For these target locations, the appropriate length of theelongated sheath body 222 depends on the distance from the targetlocation to the access site. In this configuration, the elongated sheathbody 222 is placed through an arterial access site and directedinferiorly towards the aorta.

The access sheath 220 may also include a radiopaque tip marker 230. Inan example the radiopaque tip marker is a metal band, for exampleplatinum iridium alloy, embedded near the distal end of the sheath body222 of the access sheath 220. Alternately, the access sheath tipmaterial may be a separate radiopaque material, for example a bariumpolymer or tungsten polymer blend. The sheath tip itself is configuredsuch that when the access sheath 220 is assembled with the sheathdilator 260 to form a sheath assembly, the sheath assembly can beinserted smoothly over the sheath guide wire 300 through the arterialpuncture with minimal resistance. In an embodiment, the elongated sheathbody 222 of the access sheath 220 has a lubricious or hydrophiliccoating to reduce friction during insertion into the artery. In anembodiment, the distal coating is limited to the distalmost 0.5 to 3 cmof the elongated sheath body 222, so that it facilitates insertionwithout compromising security of the sheath in the puncture site or theability of the operator to firmly grasp the sheath during insertion. Inan alternate embodiment, the sheath has no coating.

With reference to FIG. 2, in an embodiment, the arterial access sheath220 has features to aid in securement of the sheath during theprocedure. For example the access sheath 220 may have a suture eyelet234 or one or more ribs 236 molded into or otherwise attached to theadaptor 224 (located at the proximal end of the elongated sheath body222) which would allow the operator to suture tie the sheath hub to thepatient.

For a sheath adapted to be inserted into the common carotid artery forthe purpose of access to the carotid bifurcation, the length of theelongated sheath body 222 can be in the range from 7 to 15 cm, usuallybeing from 10 cm to 12 cm. The inner diameter is typically in the rangefrom 5 Fr (1 Fr=0.33 mm), to 10 Fr, usually being 6 to 8 Fr. For asheath adapted to be inserted via the common carotid artery to the midor distal internal carotid artery for the purpose of access to theintracranial or cerebral vessels, the length of the elongated sheathbody 222 can be in the range from 10 to 30 cm, usually being from 15 cmto 25 cm. The inner diameter is typically in the range from 5 Fr (1Fr=0.33 mm), to 10 Fr, usually being 5 to 6 Fr.

Particularly when the sheath is being introduced through thetranscarotid approach, above the clavicle but below the carotidbifurcation, it is desirable that the elongated sheath body 222 beflexible while retaining hoop strength to resist kinking or buckling.This is especially important in procedures that have limited amount ofsheath insertion into the artery, and there is a steep angle ofinsertion as with a transcarotid access in a patient with a deep carotidartery and/or with a short neck. In these instances, there is a tendencyfor the sheath body tip to be directed towards the back wall of theartery due to the stiffness of the sheath. This causes a risk of injuryfrom insertion of the sheath body itself, or from devices being insertedthrough the sheath into the arteries, such as guide wires. Alternately,the distal region of the sheath body may be placed in a distal carotidartery which includes one or more bends, such as the petrous ICA. Thus,it is desirable to construct the sheath body 222 such that it can beflexed when inserted in the artery, while not kinking. In an embodiment,the sheath body 222 is circumferentially reinforced, such as bystainless steel or nitinol braid, helical ribbon, helical wire, cutstainless steel or nitinol hypotube, cut rigid polymer, or the like, andan inner liner so that the reinforcement structure is sandwiched betweenan outer jacket layer and the inner liner. The inner liner may be a lowfriction material such as PTFE. The outer jacket may be one or more of agroup of materials including Pebax, thermoplastic polyurethane, ornylon.

In an embodiment, the sheath body 222 may vary in flexibility over itslength. This change in flexibility may be achieved by various methods.For example, the outer jacket may change in durometer and/or material atvarious sections. Alternately, the reinforcement structure or thematerials may change over the length of the sheath body. In oneembodiment, there is a distalmost section of sheath body 222 which ismore flexible than the remainder of the sheath body. For example, theflexural stiffness of the distalmost section is one third to one tenththe flexural stiffness of the remainder of the sheath body 222. In anembodiment, the distalmost section has a flexural stiffness (E*I) in therange 50 to 300 N-mm² and the remaining portion of the sheath body 222has a flexural stiffness in the range 500 to 1500 N-mm², where E is theelastic modulus and I is the area moment of inertia of the device. For asheath configured for a CCA access site, the flexible, distal mostsection comprises a significant portion of the sheath body 222 which maybe expressed as a ratio. In an embodiment, the ratio of length of theflexible, distalmost section to the overall length of the sheath body222 is at least one tenth and at most one half the length of the entiresheath body 222.

In some instances, the arterial access sheath is configured to access acarotid artery bifurcation or proximal internal carotid artery ICA froma CCA access site. In this instance, an embodiment of the sheath body222 has a distalmost section 223 which is 3 to 4 cm and the overallsheath body 222 is 10 to 12 cm. In this embodiment, the ratio of lengthof the flexible, distalmost section to the overall length of the sheathbody 222 is about one forth to one half the overall length of the sheathbody 222. In another embodiment, there is a transition section 225between the distalmost flexible section and the proximal section 231,with one or more sections of varying flexibilities between thedistalmost section and the remainder of the sheath body. In thisembodiment, the distalmost section is 2 to 4 cm, the transition sectionis 1 to 2 cm and the overall sheath body 222 is 10 to 12 cm, orexpressed as a ratio, the distalmost flexible section and the transitionsection collectively form at least one fourth and at most one half theentire length of the sheath body.

In some instances, the sheath body 222 of the arterial access sheath isconfigured to be inserted more distally into the internal carotid arteryrelative to the arterial access location, and possibly into theintracranial section of the internal carotid artery. For example, adistalmost section 223 of the elongated sheath body 222 is 2.5 to 5 cmand the overall sheath body 222 is 20 to 30 cm in length. In thisembodiment, the ratio of length of the flexible, distalmost section tothe overall length of the sheath body is one tenth to one quarter of theentire sheath body 222. In another embodiment, there is a transitionsection 225 between the distalmost flexible section and the proximalsection 231, in which the distalmost section is 2.5 to 5 cm, thetransition section is 2 to 10 cm and the overall sheath body 222 is 20to 30 cm. In this embodiment, the distalmost flexible section and thetransition section collectively form at least one sixth and at most onehalf the entire length of the sheath body.

Other embodiments are adapted to reduce, minimize or eliminate a risk ofinjury to the artery caused by the distal-most sheath tip facing andcontacting the posterior arterial wall. In some embodiments, the sheathhas a structure configured to center the sheath body tip in the lumen ofthe artery such that the longitudinal axis of the distal region of thesheath body is generally parallel with the longitudinal or center axisof the lumen of the vessel. In an embodiment shown in FIG. 6, the sheathalignment feature is an inflatable or enlargeable bumper, for example aballoon 608, located on an outer wall of the arterial access sheath 220.The balloon 608 may be increased in size to exert a force on inner thearterial that contacts and pushes the elongated body 222 of the aerialaccess sheath away from the arterial wall.

In another embodiment, the sheath alignment feature is one or moremechanical structures on the sheath body that can be actuated to extendoutward from the sheath tip. In an embodiment, the sheath body 222 isconfigured to be inserted into the artery such that a particular edge ofthe arterial access is against the posterior wall of the artery. In thisembodiment, the sheath alignment feature need only extend outward fromone direction relative to the longitudinal axis of the sheath body 222to lift or push the sheath tip away from the posterior arterial wall.For example, as shown in FIG. 6, the inflatable bumper 608 is a blisteron one side of the sheath body. In another example, the mechanicalfeature extends only on one side of the sheath body.

In another embodiment, at least a portion of the sheath body 222 ispre-shaped so that after sheath insertion the tip is more aligned withthe long axis of the vessel, even at a steep sheath insertion angle. Inthis embodiment the sheath body is generally straight when the dilatoris assembled with the sheath during sheath insertion over the sheathguide wire, but once the dilator and guidewire are removed, thedistalmost section of the sheath body assumes a curved or angled shape.In an embodiment, the sheath body is shaped such that the distalmost 0.5to 1 cm section is angled from 10 to 30 degrees, as measured from themain axis of the sheath body, with a radius of curvature about 0.5″. Toretain the curved or angled shape of the sheath body after having beenstraighten during insertion, the sheath may be heat set in the angled orcurved shape during manufacture. Alternately, the reinforcementstructure may be constructed out of nitinol and heat shaped into thecurved or angled shape during manufacture. Alternately, an additionalspring element may be added to the sheath body, for example a strip ofspring steel or nitinol, with the correct shape, added to thereinforcement layer of the sheath.

In an alternate embodiment, there are procedures in which it isdesirable to minimize flow resistance through the access sheath such asdescribed in U.S. Pat. No. 7,998,104 to Chang and U.S. Pat. No.8,157,760 to Criado, which are both incorporated by reference herein.FIG. 7 shows such an embodiment of the sheath body 222 where the sheathbody has stepped or tapered configuration having a reduced diameterdistal region 705 (with the reduced diameter being relative to theremainder of the sheath). The distal region 705 of the stepped sheathcan be sized for insertion into the carotid artery, typically having aninner diameter in the range from 0.065 inch to 0.115 inch with theremaining proximal region of the sheath having larger outside andluminal diameters, with the inner diameter typically being in the rangefrom 0.110 inch to 0.135 inch. The larger luminal diameter of theremainder of the sheath body minimizes the overall flow resistancethrough the sheath. In an embodiment, the reduced-diameter distalsection 705 has a length of approximately 2 cm to 4 cm. The relativelyshort length of the reduced-diameter distal section 705 permits thissection to be positioned in the common carotid artery CCA via atranscarotid approach with reduced risk that the distal end of thesheath body will contact the bifurcation B. Moreover, the reduceddiameter section also permits a reduction in size of the arteriotomy forintroducing the sheath into the artery while having a minimal impact inthe level of flow resistance. Further, the reduced distal diametersection may be more flexible and thus more conformal to the lumen of thevessel.

In some instances it is desirable for the sheath body 222 to also beable to occlude the artery in which it is positioned, for examples inprocedures that may create distal emboli. In these cases, occluding theartery stops antegrade blood flow in the artery and thereby reduces therisk of distal emboli that may lead to neurologic symptoms such as TIAor stroke. FIG. 8 shows an embodiment of an arterial access sheath 220with an inflatable balloon 805 on a distal region that is inflated viaan inflation line 810 that connect an internal inflation lumen in thesheath body 222 to a stopcock 229 which in turn may be connected to aninflation device. In this embodiment, there is also a Y-arm 815 that maybe connected to a passive or active aspiration source to further reducethe risk of distal emboli.

In some instances it is desirable to move the hemostasis valve away fromthe distal tip of the sheath, while maintaining the length of theinsertable sheath body 222 of the sheath. This embodiment is configuredto move the hands of the operator, and in fact his or her entire body,away from the target site and therefore from the image intensifier thatis used to image the target site fluoroscopically, thus reducing theradiation exposure to the user during the procedure. Essentially, thislengthens the portion of the arterial access sheath 220 that is outsidethe body. This portion can be a larger inner and outer diameter than thesheath body 222. In instances where the outer diameter of the catheterbeing inserted into the sheath is close to the inner diameter of thesheath body, the annular space of the lumen that is available for flowis restrictive. Minimizing the sheath body length is thus advantageousto minimize this resistance to flow, such as during flushing of thesheath with saline or contrast solution, or during aspiration or reverseflow out of the sheath. In an embodiment, as shown in FIG. 9, thearterial access sheath 220 has an insertable, elongated sheath body 222(i.e. the portion configured to insert into the artery) and a proximalextension portion 905. In an embodiment, the sheath body 222 has aninner diameter of about 0.087″ and an outer diameter of about 0.104″,corresponding to a 6 French sheath size, and the proximal extension hasan inner diameter of about 0.100″ to 0.125″ and an outer diameter ofabout 0.150″ to 0.175″. In another embodiment, the sheath body 222 hasan inner diameter of about 0.113″ and an outer diameter of about 0.136″,corresponding to an 8 French sheath size, and the proximal extension hasan inner diameter of about 0.125″ and an outer diameter of about 0.175″.In yet another embodiment, the sheath body 222 is stepped with a smallerdiameter distal section 705 to further reduce flow restriction, as inFIG. 7. In an embodiment, the proximal extension 905 is a lengthsuitable to meaningfully reduce the radiation exposure to the userduring a transcarotid access procedure. For example, the proximalextension 905 is between 10 and 25 cm, or between 15 and 20 cm.Alternately, the proximal extension 905 has a length configured toprovide a distance of between about 30 cm and 60 cm between thehemostasis valve 226 and the distal tip of the sheath body, depending onthe insertable length of the access sheath. A connector structure 915can connect the elongated sheath body 222 to the proximal extension 905.In this embodiment, the connector structure 915 may include a sutureeyelet 920 and/or ribs 925 to assist in securing the access sheath tothe patient. In an embodiment, the hemostasis valve 226 is a staticseal-type passive valve. In an alternate embodiment the hemostasis valve226 is an adjustable-opening valve such as a Tuohy-Borst valve 227 orrotating hemostasis valve (RHV). Alternately, the proximal extension mayterminate on the proximal end in a female Luer adaptor to which aseparate hemostasis valve component may be attached, either a passiveseal valve, a Tuohy-Borst valve or rotating hemostasis valve (RHV).

Typically, vessel closure devices requires an arterial access sheathwith a maximum distance of about 15 cm between distal tip of the sheathbody to the proximal aspect of the hemostasis valve, with sheath body222 of about 11 cm and the remaining 4 cm comprising the length of theproximal hemostasis valve; thus if the access sheath has a distance ofgreater than 15 cm it is desirable to remove the proximal extension 905at the end of the procedure. In an embodiment, the proximal extension905 is removable in such a way that after removal, hemostasis ismaintained. For example a hemostasis valve is built into the connector915 between the sheath body 222 and the proximal extension 905. Thehemostasis valve is opened when the proximal extension 905 is attachedto allow fluid communication and insertion of devices, but preventsblood flowing out of the sheath when the proximal extension 905 isremoved. After the procedure is completed, the proximal extension 905can be removed, reducing the distance between the proximal aspect of thehemostasis valve and sheath tip from greater than 15 cm to equal or lessthan 15 cm and thus allowing a vessel closure device to be used with theaccess sheath 220 to close the access site.

In some procedures it may be desirable to have a low resistance (largebore) flow line or shunt connected to the access sheath, such asdescribed in U.S. Pat. No. 7,998,104 to Chang and U.S. Pat. No.8,157,760 to Criado, which are both incorporated by reference herein.The arterial sheath embodiment shown in FIG. 10 has a flow line 1005with internal lumen to a Y-arm 1015 of the connector 915. This flow linehas a lumen fluidly connected to a lumen in the sheath body. The flowline 1005 may be connected to a lower pressure return site such as avenous return site or a reservoir. The flow line 1005 may also beconnected to an aspiration source such as a pump or a syringe. In anembodiment, an occlusion element may also be included on the distal endof the sheath body 222, for example an occlusion balloon. This may bedesirable in percutaneous procedures, where the vessel cannot beoccluded by vascular surgical means such as vessel loops or vascularclamps.

In some procedures, it may be desirable to limit the amount of sheathbody insertion into the artery, for example in procedures where thetarget area is very close to the arterial access site. In a stentprocedure of the carotid artery bifurcation, for example, the sheath tipshould be positioned proximal of the treatment site (relative to theaccess location) so that it does not interfere with stent deployment orenter the diseased area and possibly cause emboli to get knocked loose.In an embodiment of arterial sheath 220 shown in FIGS. 11A and 11B, asheath stopper 1105 is slideably connected or mounted over the outsideof the distal portion of the sheath body. The sheath stopper 1105 isshorter than the distal portion of the sheath, effectively shorteningthe insertable portion of the sheath body 222 by creating a positivestop at a certain length along the sheath body 222. The sheath stopper1105 may be a tube that slidably fits over the sheath body 222 with alength that, when positioned on the sheath body 222, leaves a distalportion of the sheath body exposed. This length can be in the range 2 to4 cm. More particularly, the length is 2.5 cm. The distal end of thesheath stopper 1105 may be angled and oriented such that the angle sitsflush with the vessel and serves as a stop against the arterial wallwhen the sheath is inserted into the artery when the vessel is insertedinto the artery, as shown in FIG. 11A. Alternately, the distal end ofthe sheath stopper may be formed into an angled flange 1115 thatcontacts the arterial wall, as shown in FIG. 11B. The flange 1115 isrounded or has an atraumatic shape to create a more positive andatraumatic stop against the arterial wall. The sheath stopper 1105 maybe permanently secured to the arterial sheath, for example the proximalend of the sheath stopper may be adhered to connector 915 of thearterial access sheath. Alternately, the sheath stopper 1105 may beremovable from the arterial access sheath 220 by the user so it can beoptionally utilized in a procedure. In this instance, the sheath stopper1105 may have a locking feature on the proximal portion that engageswith a corresponding locking features on the connector 915, for exampleslots or recesses on the proximal sheath stopper engaging protrusions onthe connector. Other locking features may also be utilized.

In situations where the insertion of the sheath body is limited tobetween 2 and 3 cm, and particularly when the sheath body is inserted ata steep angle, the sheath may conform to a bayonet shape when secured tothe patient. For example, the bayonet shape may comprise a first portionthat extends along a first axis and a second portion that extends alonga second axis that is axially offset from the first axis and/ornon-parallel to the first axis. The springiness of the sheath bodycauses this shape to exert a force on the vessel at the site ofinsertion and increase the tendency of the sheath to come out of thevessel if not properly secured. To reduce the stress on the vessel, thesheath stopper may be pre-shaped into a curved or bayonet shape so thatthe stress of the sheath body when curved is imparted onto the sheathstopper rather than on the vessel. The sheath stopper may be made fromspringy but bendable material or include a spring element such as astainless steel or nitinol wire or strip, so that when the dilator isinserted into the sheath and sheath stopper assembly, the sheath isrelatively straight, but when the dilator is removed the sheath stopperassumes the pre-curved shape to reduce the force the sheath imparts onthe vessel wall. Alternately, the sheath stopper may be made ofmalleable material or include a malleable element such as a bendablemetal wire or strip, so that it can be shaped after the sheath isinserted into a desired curvature, again to reduce the stress the sheathimparts on the vessel wall.

Sheath Dilator

With reference again to FIG. 2, the sheath dilator 260 is a component ofthe transcarotid access sheath system 200. The sheath dilator 260 is anelongated body that is inserted into the artery and enables smoothinsertion of the access sheath 220 over the sheath guidewire 300 througha puncture site in the arterial wall. Thus, the distal end of thedilator 260 is generally tapered to allow the dilator to be insertedover the sheath guidewire 300 into the artery, and to dilate the needlepuncture site to a larger diameter for insertion of the access sheath220 itself. To accommodate these functions, the dilator 260 has atapered end 268 with a taper that is generally between 6 and 12 degreestotal included angle (relative to a longitudinal axis of the dilator),with a radiused leading edge. Sheath dilators are typically locked tothe access sheath when assembled for insertion into the artery. Forexample a proximal hub 264 of the sheath dilator 260 is structured tosnap into or over a corresponding structure on the hemostasis valve 226of the arterial access sheath 220. An inner lumen of the dilator 260accommodates a sheath guidewire 300, with an inner diameter of between0.037 to 0.041″, depending on the sheath guide wire size for example.

For a transcarotid access sheath system 200, it may be desirable to makethe distal section of the sheath dilator 260 more flexible, tocorrespond with an increased flexible section of the access sheath 220.For example, the distal 2 to 5 cm of the sheath dilator 260 may be 20 to50% more flexible than the proximal portion of the sheath dilator 260.This embodiment would allow a sheath and dilator being inserted toaccommodate a steep insertion angle, as is often the case in atranscarotid access procedure, with a smoother insertion over theguidewire while still maintaining columnar support of the dilator. Thecolumnar support is desirable to provide the insertion force required todilate the puncture site and insert the access sheath.

For some transcarotid access sheath systems, it may be desirable to alsouse a smaller diameter access guidewire (for example in the range 0.014″to 0.018″ diameter) to guide the sheath and dilator into the artery. Inthis embodiment, the sheath dilator tapered end 268 is configured toprovide a smooth transition from a smaller wire size to the accesssheath. In one variation, the sheath guide wire is 0.018″ and the innerdilator lumen is in the range 0.020″-0.022″. In another variation, thesheath guide wire is 0.014″ and the inner dilator lumen is in the range0.016″ to 0.018″. The taper is similarly modified, for example the taperlength is longer to accommodate a taper from a smaller diameter to theinner diameter of the access sheath, or may comprise two taper angles toprovide a smooth transition from the smaller diameter wire to the accesssheath without overly lengthening the overall length of the taper.

In some procedures, it is desirable to position the distal tip of thesheath body 222 of the arterial access sheath 220 in the mid to distalcervical, petrous, or cavernous segments of the ICA as described above.These segments have curvature often greater than 90 degrees. In may bedesirable to have a sheath dilator with a softer and longer taper, to beable to navigate these bends easily without risk of injury to thearteries. However, in order to insert the sheath through the arterialpuncture, the dilator desirably has a certain stiffness and taper toprovide the dilating force. In an embodiment, the transcarotid accesssheath system 200 is supplied or included in a kit that includes two ormore tapered dilators 260A and 260B. The first tapered dilator 260A isused with the arterial access device to gain entry into the artery, andis thus sized and constructed in a manner similar to standard introducersheath dilators. Example materials that may be used for the tapereddilator include, for example, high density polyethylene, 72D Pebax, 90DPebax, or equivalent stiffness and lubricity material. A second tapereddilator 260B of the kit may be supplied with the arterial access devicewith a softer distal section or a distal section that has a lowerbending stiffness relative to the distal section of the first tapereddilator. That is, the second dilator has a distal region that is softer,more flexible, or articulates or bends more easily than a correspondingdistal region of the first dilator. The distal region of the seconddilator thus bends more easily than the corresponding distal region ofthe first dilator. In an embodiment, the distal section of the firstdilator 260A has a bending stiffness in the range of 50 to 100 N-mm² andthe distal section of the second dilator 260B has a bending stiffness inthe range of 5 to 15 N-mm².

The second dilator 260B (which has a distal section with a lower bendingstiffness) may be exchanged with the initial, first dilator such thatthe arterial access device may be inserted into the internal carotidartery and around curvature in the artery without undue force or traumaon the vessel due to the softer distal section of the second dilator.The distal section of the soft, second dilator may be, for example, 35or 40D Pebax, with a proximal portion made of, for example 72D Pebax. Anintermediate mid portion or portions may be included on the seconddilator to provide a smooth transition between the soft distal sectionand the stiffer proximal section. In an embodiment, one or both dilatorsmay have radiopaque tip markers so that the dilator tip position isvisible on fluoroscopy. In one variation, the radiopaque marker is asection of tungsten loaded Pebax or polyurethane which is heat welded tothe distal tip of the dilator. Other radiopaque materials may similarlybe used to create a radiopaque marker at the distal tip.

To facilitate exchange of the first dilator for the second dilator, oneor both dilators may be configured such that the distal section of thedilator is constructed from a tapered single-lumen tube, but theproximal portion of the dilator and any adaptor on the proximal end hasa side opening. FIG. 12 shows an example of a dilator 1205 formed of anelongated member sized and shaped to be inserted into an artery, and aproximal hub 1210. The dilator has a side opening 1215, such as a slot,that extends along at least a portion of the length of the dilator 1205such as along the elongated body and the proximal hub 1210. In anembodiment, the side opening 1215 is located only on a proximal regionof the dilator 1205 and through the proximal hub 1210 although this mayvary. The side opening 1215 provides access to an internal lumen of thedilator 1205, such as to insert and/or remove a guidewire into or fromthe lumen. An annular, movable sleeve 1220 with a slot on one side islocated at or near the proximal hub 1210 of the dilator 1205. The sleeve1220 may be moved, such as via rotation, about a longitudinal axis ofthe hub 1210, as described below. Note that the distal end of thedilator 1205 has a tapered configuration for dilating tissue.

FIG. 13 shows an enlarged view of the proximal region of the dilator1205. As mentioned, the dilator 1205 has a side opening 1215 in the formof a slot that extends along the length of the dilator 1205 and theproximal hub 1210. The sleeve 1220 is positioned around the outerperiphery of the dilator and is shaped such that it covers at least aportion of the side opening 1215. Thus, the sleeve 1220 can prevent aguidewire positioned inside the dilator 1205 from exiting the dilatorvia the side opening 1215. As mentioned, the sleeve 1220 is rotatablerelative to the dilator 1205 and proximal hub 1210. In the illustratedembodiment, the sleeve 1220 is rotatable about a longitudinal axis ofthe dilator 1205 although other types of relative movement are withinthe scope of this disclosure. As shown in FIG. 14, the sleeve 1220 has aslot 1225 that can be aligned with the side opening 1215. When alignedas such, the slot 1225 and side opening 1215 collectively provide anopening for a guidewire to be inserted or removed from the internallumen of the dilator 1205. The sleeve 1220 can be rotated between theposition shown in FIG. 13 (where it covers the side opening 1215) andthe position shown in FIG. 14 (where the side opening is uncovered dueto the slot 1225 being aligned with the side opening 1215.)

A method of use of this embodiment of an access sheath kit is nowdescribed. A sheath guide wire, such as an 0.035″ guidewire, is insertedinto the common carotid artery, either using a Modified Seldingertechnique or a micropuncture technique. The distal end of the guidewirecan be positioned into the internal or external carotid artery, or stopin the common carotid artery short of the bifurcation. The arterialaccess sheath with the first, stiffer dilator, is inserted over the0.035″ wire into the artery. The arterial access sheath is inserted suchthat at least 2.5 cm of sheath body 222 is in the artery. If additionalpurchase is desired, the arterial access sheath may be directed further,and into the internal carotid artery. The first dilator is removed whilekeeping both the arterial access sheath and the 0.035″ wire in place.The side opening 1215 in the proximal portion of the dilator allows thedilator to be removed in a “rapid exchange” fashion such that most ofthe guidewire outside the access device may be grasped directly duringdilator removal. The second dilator is then loaded on to the 0.035″ wireand inserted into the sheath. Again, a dilator with a side opening 1215in the proximal portion of the dilator may be used to allow the 0.035″wire to be grasped directly during guide wire insertion in a “rapidexchange” technique. Once the second dilator is fully inserted into thearterial access device, the arterial access sheath with the softertipped, second dilator is advanced up the internal carotid artery andaround bends in the artery without undue force or concern for vesseltrauma. This configuration allows a more distal placement of thearterial access sheath without compromising the ability of the device tobe inserted into the artery.

Alternately, one or more standard dilators may be used without sideopenings. If a standard dilator without a side opening is used, afterthe access device is inserted into the artery over a guide wire with thefirst dilator, the first dilator may be removed together with theguidewire, leaving only the access device in place. The second dilatorwith a guide wire preloaded into the central lumen may be insertedtogether into the arterial access device. Once fully inserted, theaccess device and second dilator with softer tip may be advanceddistally up the internal carotid artery as above. In this alternatemethod, the initial guide wire may be used with both dilators, or may beexchanged for a softer tipped guide wire when inserted with the secondsofter tipped dilator.

In some instances, it may be desirable to insert the access sheathsystem over an 0.035″ wire into the carotid artery, but then exchangethe wire to a smaller guidewire, in the range 0.014″ to 0.018″. Becausethe access into the carotid artery may require a steep angle of entry, awire that can offer good support such as an 0.035″ wire may be desirableto initially introduce the access sheath into the CCA. However, once thesheath is in the artery but the user would like to advance it furtherover a smaller guidewire, it may be desirable to exchange the 0.035″wire for a smaller guide wire. Alternately, the user may exchange boththe dilator and 0.035″ wire for a softer dilator and smaller guide wirein the range 0.014″ to 0.018″. Alternately, the user may wish toposition an 0.014″ guidewire which he or she will subsequently tointroduce an interventional device, while the sheath and dilator arestill in place. The dilator may offer access and support for this guidewire, and in instances of severe access sheath angle may aid indirecting the wire away from the posterior wall of the artery so thatthe wire may be safely advanced into the vascular lumen without risk ofluminal injury.

In an embodiment as shown in FIG. 15, the sheath dilator 260 is atwo-part dilator assembly, with an inner dilator 269 and an outerdilator 270 that slidably attach to one another in a co-axialarrangement. Both dilators have proximal hubs 264 a and 264 b. When thetwo dilators are assembled together, the two hubs 264 a and 264 b havefeatures which allow them to be locked together, e.g. a snap fit or athreaded fit, so that the two dilators can be handled as one unit. In anembodiment, the inner dilator 269 has a proximal hub 264 b whichincludes a rotating coupler with internal threads that engage externalthreads on the proximal hub 264 a of the outer dilator 270. The innerdilator 269 effectively transforms the dilator assembly from an 0.035″or 0.038″ wire compatible dilator to an 0.018″ or 0.014″ wire compatibledilator, and extends out the distal end of the outer dilator. In anembodiment, shown in FIG. 16, the inner dilator has an angled tip 276that is bent or angled relative to a longitudinal axis of the remainderof the dilator. In an embodiment, the angle is a 45 degree angle. Thisangled tip 276 allows the user to direct the guidewire into one oranother branch vessel more easily. The inner dilator may have a taperedtip, straight as shown in FIG. 15 or an angled tip as shown in FIG. 16.Alternately, the inner dilator may have a constant outer diameter to thedistal end, with a rounded leading edge. In an embodiment, the innerdilator has a radiopaque marker 274 at or near the distal tip to aid invisualization of the dilator under fluoroscopy. In an embodiment, theinner dilator is reinforced to make it more torquable to aid indirecting the angled tip in a particular direction. For example thedilator may have a coil or braid reinforcement layer. Once theinterventional wire is positioned, the two-part dilator is removed andthe wire may then be used to insert interventional devices through thearterial sheath into the artery and advanced to the treatment site.

An alternate embodiment, shown in FIG. 17, allows two separate wiresizes to be used with the dilator. This embodiment includes a dilator1705 with two guide wire internal lumens that extend along the length ofthe device. FIG. 17 shows the distal end of this embodiment. As seenmore clearly in a cross sectional view FIG. 18, one lumen 1805 isconfigured for an 0.035″ or 0.038″ guidewire, and the other lumen 1815is for a an 0.014″ to 0.018″ guide wire. In this embodiment, the largerlumen 1805 is centered around the centerline of the taper 268, whereasthe smaller lumen 1815 is offset from the centerline of the taper. Inthis configuration, the access sheath is introduced into the artery overthe larger guidewire, which is positioned in the larger lumen 1805. Oncepositioned, an interventional wire can be placed through the secondlumen 1815. The larger guidewire and dilator are then removed from theaccess sheath and the interventional wire may then be used to insertinterventional devices through the arterial sheath into the artery andadvanced to the treatment site as above.

Sheath Guidewire

Arterial access sheaths are typically introduced into the artery over asheath guidewire of 0.035″ or 0.038″ diameter. The inner diameter andtaper length of the distal tip of the dilator are sized to fit with sucha guidewire. Some sheaths, for example for radial artery access, aresized to accommodate a sheath guidewire of 0.018″ diameter, with acorresponding dilator having a distal tip inner diameter and taperlength. The sheath guidewire may have an atraumatic straight, angled, orJ-tip. The guidewire smoothly transitions to a stiffer segment on theproximal end. This configuration allows atraumatic entry and advancementof the wire into the artery while allowing support for the sheath whenthe sheath is introduced into the artery over the wire. Typically thetransition from the atraumatic tip is about 4 to 9 cm to the stiffersection. The sheath is usually inserted 15 to 20 cm into the artery, sothat the stiffer segment of the wire is at the arterial entry site whenthe sheath is being inserted.

However, in the case of a transcarotid access entry point, the amount ofwire that can be inserted is much less than 15 cm before potentiallycausing harm to the distal vessels. In a case of a transcarotid accessfor a carotid stent or PTA procedure, it is very important that the wireinsertion length is limited, to avoid risk of distal emboli beinggenerated by the sheath guide wire at the site of carotid arterydisease. Thus it is desirable to provide a guide wire that is able toprovide support for a potentially steep sheath entry angle while beinglimited in length of insertion. In an embodiment, a transcarotid sheathguidewire has an atraumatic tip section but have a very distal and shorttransition to a stiffer section. For example, the soft tip section is1.5 to 2.5 cm, followed by a transition section with length from 3 to 5cm, followed by a stiffer proximal segment, with the stiffer proximalsection comprising the remainder of the wire.

The sheath guidewire may have guide wire markings 318 to help the userdetermine where the tip of the wire is with respect to the dilator. Forexample, there may be a marking on the proximal end of the wirecorresponding to when the tip of the wire is about to exit the microaccess cannula tip. This marking would provide rapid wire positionfeedback to help the user limit the amount of wire insertion. In anotherembodiment, the wire may include an additional mark to let the user knowthe wire has existed the cannula by a set distance, for example 5 cm.

Micro Access Components

With reference to FIG. 1, a micro access kit 100 for initialtranscarotid access includes an access needle 120, an access guidewire140, and a micro access cannula 160. The micro access cannula 160includes a body 162 and an inner dilator 168 slidably positioned withina lumen of the body 162. Typically for arterial access, the initialneedle puncture may be with a 21G or 22G access needle, or an 18G needleif the Modified Seldinger technique is used. For transcarotid access, itmay be desirable to access with an even smaller needle puncture.Percutaneous access of the carotid artery is typically more challengingthan of the femoral artery. The carotid artery is a thicker-walledartery, it is surrounded by a tissue sleeve known as the carotid sheath,and it is not anchored down as much by surrounding musculature,therefore the initial needle stick is more difficult and must be donewith more force, onto an artery that is less stable, thus increasing therisk of mis-placed puncture, arterial dissection, or back wall puncture.A smaller initial needle puncture, for example a 23G or 24G needle,increases the ease of needle entry and reduce these risks. The sheathguidewire should be accordingly sized to fit into the smaller needle,for example a 0.016″ or 0.014″ wire. The access needle 120 may include atextured surface on the distal end to render it visible on ultrasound,to aid in ultrasound-guided insertion of the needle into the artery. Theneedle length may be in a range from 4 cm to 8 cm in length.

Similarly to sheath guide wires, micro access guide wires have atransition segment from a floppy distal tip to a core section that isstiffer than the distal tip or distal region. Such micro accessguidewires are typically 0.018″ in diameter, with a floppy, distalsegment of about 1-2 cm, and a transition zone of 5-6 cm to the stiffersegment. In an embodiment, a transcarotid access guidewire is from0.014″ to 0.018″ in diameter, and has a floppy segment of 1 cm, atransition zone of 2-3 cm to bring the stiff supportive section muchcloser to the distal tip. This will allow the user to have good supportfor his micro access cannula insertion even in steep access angles andlimitations on wire insertion length.

As with the sheath guide wire, the micro access guide wire may haveguide wire markings 143 to help the user determine where the tip of thewire is with respect to the micro cannula. For example, a marking can belocated on the proximal end of the wire corresponding to when the tip ofthe wire is about to exit the micro cannula. This marking would providerapid wire position feedback to help the user limit the amount of wireinsertion. In another embodiment, the wire may include an additionalmark to let the user know the wire has existed the dilator by a setdistance, for example 5 cm.

The micro access cannula itself may be configured for transcarotidinsertion. Typically, the micro access cannula 160 includes a cannula162 and an inner dilator 168 with a tapered tip. The inner dilator 168provides a smooth transition between the cannula and the access guidewire. The cannula is sized to receive the 0.035″ wire, with innerdiameter in the range 0.038″ to 0.042″. In an embodiment, a micro accesscannula 160 is configured for transcarotid access. For example thedilator of the cannula may be sized for a smaller 0.014″ access guidewire 140. Additionally, the cannula itself may have depth marking to aidthe user in limiting the amount of insertion. In an embodiment, themicro access cannula 160 has a radiopaque marker 164 at the distal tipof the cannula 162 to help the user visualize the tip location underfluoroscopy. This is useful for example in cases where the user may wantto position the cannula in the ICA or ECA, for example.

Exemplary Kits:

Any or all of the devices described above may be provided in kit form tothe user such that one or more of the components of the systems areincluded in a common package or collection of packages. An embodiment ofan access sheath kit comprises an access sheath, sheath dilator, andsheath guidewire all configured for transcarotid access as describedabove.

In an embodiment, a micro access kit comprises an access needle, a microaccess guide wire, and a micro access cannula and dilator wherein theguidewire is 0.014″ and the micro access cannula and dilator are sizedto be compatible with the 0.014″ guide wire.

In an embodiment, an access kit comprises the access sheath, sheathdilator, sheath guide wire, access needle, micro access guide wire andmicro access cannula and dilator, all configured for transcarotidaccess.

In an alternate embodiment, the access guidewire is also used as thesheath guide wire. In this embodiment, the access kit comprises anaccess needle, access guide wire, access sheath and dilator. The sheathand dilator use the access guide wire to be inserted into the vessel,thereby avoiding the steps required to exchange up to a larger sheathguidewire. In this embodiment, the dilator taper length and inner lumenis sized to be compatible with the smaller access guide wire. In oneembodiment the access guide wire is 0.018″. In an alternate embodimentthe access guide wire is 0.016″. In an alternate embodiment, the accessguide wire is 0.014″.

Exemplary Methods:

There are now described exemplary methods of use for a transcarotidaccess system. In an exemplary transcarotid procedure to treat a carotidartery stenosis, the user starts by performing a cut down to the commoncarotid artery. The user then inserts an access needle 120 into thecommon carotid artery at the desired access site. An access guide wire140 with a taper configured for transcarotid access is inserted throughthe needle into the common carotid artery and advanced into the CCA. Theaccess needle 120 is removed and a micro access cannula 160 is insertedover the wire 140 into the CCA. The micro access cannula is inserted adesired depth using the marks 166 on the cannula as a guide, to preventover insertion.

The user removes the cannula inner dilator 168 and guide wire 140,leaving the cannula 162 in place. If desired, the user performs anangiogram through the cannula 162. The user then places sheath guidewire 300 through the cannula, using guide wire markings 318 to aid ininserting the wire to a desired insertion length. The cannula 162 isremoved from the guidewire and the access sheath 220 and sheath dilator260 are inserted as an assembly over the sheath guidewire 300 into theCCA. The sheath stopper flange 1115 of the sheath stopper 1105 limitsthe insertion length of the arterial sheath. Once positioned, thedilator 260 and guidewire 300 are removed. The sheath is then sutured tothe patient using the securing eyelets 234 and/or ribs 236. Aninterventional procedure is then performed by introduction ofinterventional devices through hemostasis valve 226 on the proximal endof the arterial sheath and to the desire treatment site. Contrastinjections may be made as desired during the procedure via the flush arm228 on the arterial sheath 220.

Alternately, the sheath guidewire 300 is placed into the CCA via asingle needle puncture with a larger access needle, for example an 18Gneedle. In this embodiment, the access cannula and access guide wire arenot needed. This embodiment reduces the number of steps required toaccess the artery, and in some circumstances may be desirable to theuser.

Alternately, the sheath dilator is a two-part sheath dilator assembly260 as shown in FIG. 15, with an inner dilator 269 and an outer dilator270. The outer dilator 270 is configured to receive an 0.035″ sheathguide wire 300 and to provide a smooth transition from the 0.035″ wireto the access sheath 220. The inner dilator 269 is configured to receivea smaller guide wire in the range 0.014″ to 0.018″ and to provide asmooth transition from the smaller guide wire to the outer dilator 270.Once the sheath guidewire is positioned in the CCA, the access sheathand outer sheath dilator 270 are inserted over an 0.035″ sheathguidewire 300 into the CCA. The guidewire is then removed and an innersheath dilator 269 is inserted into the outer sheath dilator. In anembodiment, the inner sheath dilator has an angled tip 276 as seen inFIG. 16. An interventional 0.014″ guide wire is inserted through theinner sheath dilator and is directed to the target treatment site usingthe angled tip to aid in guide wire positioning. Alternately, the innersheath dilator has a straight tip and is used to aid in positioning theguide wire safely into the CCA. Once the 0.014″ wire is positioned at oracross the target treatment site, the sheath dilator 260 and sheath0.035″ guide wire 300 are then removed, and the intervention proceeds.

In an alternate embodiment, the sheath dilator is a two lumen sheathdilator 1705. In this embodiment, the sheath and dilator are insertedover the sheath guide wire 300, with the sheath guidewire positioned inthe larger lumen 1805 of dilator 1705. Once the sheath and dilator is inplace, an interventional 0.014″ guide wire is positioned through thesmaller lumen 1815. The dilator provides distal support and maintainsthe position of the sheath tip in the axial direction of the vessellumen, thus allowing a potentially safer and easier advancement of the0.014″ wire than if the dilator were removed and the sheath tip wasdirected at least partially towards to posterior wall of the artery.Once the 0.014″ wire is positioned at or across the target treatmentsite, the sheath dilator 1705 and sheath guide wire 0.035″ are thenremoved, and the intervention proceeds.

In yet another embodiment, it may be desirable to occlude the CCA duringthe intervention to minimize antegrade flow of emboli. In thisembodiment, the occlusion step may be performed via vascular surgicalmeans such as with a vessel loop, tourniquet, or vascular clamp. In analternate embodiment, the access sheath 220 has an occlusion elementsuch as an occlusion balloon 250 on the distal tip. In this embodiment,the balloon is inflated when CCA occlusion is desired. In a furthervariant, while the CCA is occluded either surgically or via balloonocclusion, it may be desirable to connect the arterial sheath to a flowshunt, for example to create a reverse flow system around the area ofthe treatment site to minimize distal emboli. In this embodiment, thearterial sheath 220 has a Y connection to a flow line 256. The flow linemay be connected to a return site with a pressure lower than arterialpressure to create a pressure gradient that results in reverse flowthrough the shunt, for example an external reservoir or a central venousreturn site like the femoral vein or the internal jugular vein.Alternately, the flow line may be connected to an aspiration source suchas an aspiration pump or syringe.

In another embodiment, a transcarotid access system is used to perform apercutaneous neurointerventional procedure. In this embodiment, the userperforms a percutaneous puncture of the common carotid artery CCA withan access needle 120 at the desired access site. Ultrasound may be usedto accurately identify a suitable access site and guide the needlepuncture. An access guide wire 140 is inserted through the needle intothe common carotid artery and advanced into the CCA. The access needle120 is removed and a micro access cannula 160 is inserted over the wire140 into the CCA. The user removes the cannula inner dilator 168 andguide wire 140, leaving the cannula 162 in place. If desired, the userperforms an angiogram through the cannula 162. The user then placessheath guide wire 300 through the cannula, using guide wire markings 318to aid in desired insertion length. The cannula 162 is removed from theguidewire and the access sheath 220 and sheath dilator 260 are insertedas an assembly over the sheath guidewire 300 into the CCA.

Alternately, the smaller access guide wire 140 is used to position theaccess sheath 220 and sheath dilator 260 into the CCA. In thisembodiment, the sheath dilator tapered tip 266 has been configured totransition smoothly from the access guide wire 140 to the access sheath220. In one variant, the access needle is 21G and the access guide wireis 0.018″. In another variant, the access needle is 24G and the accessguide wire is 0.014″. Once the sheath is placed, the guide wire andsheath dilator are removed and an interventional procedure is thenperformed by introduction of interventional devices through hemostasisvalve 226 on the proximal end of the arterial sheath and to the desiretreatment site. Contrast injections may be made as desired during theprocedure via the flush arm 228 on the arterial sheath 220.

Alternately, it may be desirable once the sheath is placed in the CCA toadvance it further into the ICA, for example in the mid to distalcervical ICA, petrous ICA or further distally. In this embodiment, thesheath dilator may be replaced with a softer sheath dilator so that thesheath may be advanced without risk of damaging the distal ICA. In thisembodiment, the softer dilator has a distal radiopaque marker so thatthe user may easily visualize the leading edge of the sheath and dilatorassembly during positioning of the sheath. Once the access sheath ispositioned, the dilator and sheath guide wire may be removed and theintervention can proceed. Alternately, once the sheath is placed in theCCA, the 0.035″ guide wire may be removed and an inner dilator with asmaller guide wire in the range 0.014″ to 0.018″ may be inserted intosheath dilator. The sheath dilator assembly with the inner dilator andsmaller guide wire may be then positioned more distally in the ICA withreduced risk of vessel trauma.

In an embodiment, it may be desirable to occlude the CCA or ICA duringportions of the procedure to reduce the chance of distal emboli flowingto the brain. In this embodiment, the CCA or ICA is occluded by means ofan occlusion balloon 250 on the access sheath 220. It may also bedesirable to connect the arterial sheath to a flow shunt, for example tocreate a reverse flow system around the area of the treatment site tominimize distal emboli. In this embodiment, the arterial sheath 220 hasa Y connection to a flow line 256. The flow line may be connected to areturn site with a pressure lower than arterial pressure to create apressure gradient that results in reverse flow through the shunt.Alternately, the flow line may be connected to an aspiration source suchas an aspiration pump or syringe.

While this specification contains many specifics, these should not beconstrued as limitations on the scope of an invention that is claimed orof what may be claimed, but rather as descriptions of features specificto particular embodiments. Certain features that are described in thisspecification in the context of separate embodiments can also beimplemented in combination in a single embodiment. Conversely, variousfeatures that are described in the context of a single embodiment canalso be implemented in multiple embodiments separately or in anysuitable sub-combination. Moreover, although features may be describedabove as acting in certain combinations and even initially claimed assuch, one or more features from a claimed combination can in some casesbe excised from the combination, and the claimed combination may bedirected to a sub-combination or a variation of a sub-combination.Similarly, while operations are depicted in the drawings in a particularorder, this should not be understood as requiring that such operationsbe performed in the particular order shown or in sequential order, orthat all illustrated operations be performed, to achieve desirableresults.

Although embodiments of various methods and devices are described hereinin detail with reference to certain versions, it should be appreciatedthat other versions, embodiments, methods of use, and combinationsthereof are also possible. Therefore the spirit and scope of theappended claims should not be limited to the description of theembodiments contained herein.

The invention claimed is:
 1. A method for introducing an interventionaldevice into a common carotid artery, the method comprising: introducingan arterial access sheath and a first dilator into a common carotidartery via a carotid access needle puncture site while the first dilatoris positioned within the arterial access sheath, and wherein: a) thearterial access sheath includes a sheath body sized and shaped to beintroduced into the common carotid artery via the carotid artery accesssite, the sheath body defining an internal delivery lumen; and b) thefirst dilator has a tapered distal tip sized and shaped to dilate theneedle puncture site to a diameter sufficient for insertion of thearterial access sheath into the artery, the first dilator having a firstinternal guidewire lumen, wherein at least a portion of the firstdilator has a first bending stiffness; removing the first dilator fromthe arterial access sheath; and introducing an elongated second dilatorinto the internal delivery lumen while the sheath body is positionedwithin the common carotid artery, the second dilator having a tapereddistal tip, the second dilator having a second internal guidewire,wherein the second dilator has a distal region having a second bendingstiffness less than the first bending stiffness of the first dilator. 2.A method as in claim 1, wherein the first dilator has a distal sectionthat is more flexible than a proximal section of the first dilator so asto accommodate a steep insertion angle into an artery.
 3. A method as inclaim 2, wherein the distal section of the first dilator is 2 to 5 cm inlength.
 4. A method as in claim 2, wherein the distal section of thefirst dilator is 20% to 50% more flexible than the proximal section ofthe first dilator.
 5. A method as in claim 1, wherein the distal regionof the second dilator is more flexible than a distal section of thefirst dilator.
 6. A method as in claim 1, wherein the distal region ofthe second dilator is 2 to 5 cm in length.
 7. A method as in claim 1,wherein the distal region of the second dilator is 20% to 50% moreflexible than a proximal region of the second dilator.
 8. A method as inclaim 1, wherein the second dilator has an intermediate mid portion thatprovides a smooth transition in stiffness between a proximal region ofthe second dilator and the distal region of the second dilator.
 9. Amethod as in claim 1, wherein a distal region of the first dilator has abending stiffness in the range of 50 to 100 N-mm² and the distal regionof the second dilator has a bending stiffness in the range of 5 to 15N-mm².
 10. A method as in claim 1, further comprising a radiopaque tipmarker on at least one of the first and second dilators.
 11. A method asin claim 1, wherein the second internal guidewire lumen has a diameterthat is smaller than a diameter of the first internal guidewire lumen.12. A method as in claim 1, wherein the first internal guidewire lumenaccommodates a guidewire of 0.035 to 0.038 inch in diameter and thesecond internal guidewire lumen accommodates a guidewire of 0.014 to0.018 inch in diameter.
 13. A method as in claim 1, wherein a proximalregion of at least one of the first dilator and the second dilatorincludes a hub having a side opening that provides access to theinternal lumen of the respective dilator to permit insertion and removalof a guidewire into or from the internal lumen of the respectivedilator.
 14. A method as in claim 13, wherein the hub includes a sleevethat moves between a first position that covers the side opening and asecond position that does not cover the side opening.
 15. A method as inclaim 1, wherein the second dilator is a two-part dilator formed of anouter dilator and one or more inner dilators that slidably attach to theouter dilator in a co-axial arrangement.
 16. A method as in claim 15,wherein the outer dilator accommodates a guidewire of 0.035 to 0.038inch in diameter and inner dilator accommodates a guidewire of 0.014 to0.018 inch in diameter.
 17. A method as in claim 15, wherein the innerand outer dilators include proximal hubs that lock to one another tolock the inner and outer dilators to one another.
 18. A method as inclaim 15, wherein at least one of the inner dilators has an angled tipthat angles away from a longitudinal axis of the respective dilator. 19.A method as in claim 1, wherein the sheath body has a proximal sectionand a distalmost section that is more flexible than the proximalsection, and wherein a ratio of an entire length of the distalmostsection to an overall length of the sheath body is one tenth to one halfthe overall length of the sheath body.
 20. A method as in claim 1,wherein the sheath body has a proximal section and a distalmost sectionthat is more flexible than the proximal section, and wherein thedistalmost section is 2.5 to 5 cm in length and the overall sheath bodyis 20 to 30 cm in length.
 21. A method as in claim 1, wherein the sheathbody has a proximal section and a distalmost section that is moreflexible than the proximal section and a transition section between thedistalmost flexible section and the proximal section and wherein thedistalmost section is 2.5 to 5 cm in length, the transition section is 2to 10 cm in length, and the overall sheath body is 20 to 30 cm inlength.
 22. A method as in claim 1, wherein at least one of the firstand second dilators is configured to lock to the arterial access sheathwhen positioned in the internal lumen of the arterial access sheath.